<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        table,td{
            border:3px solid green;
        }
        table{
            /* 折叠边框 */
            border-collapse:collapse;
            width: 400px;
            height: 400px;
        }
        td{
            /* 水平居中 */
            text-align:center;
            background-color:blueviolet;
            color:white;
        }

    </style>
</head>
<body>
    <table>
        <tr>
            <td>单元格</td>
            <td>单元格</td>
            <td>单元格</td>
        </tr>
        <tr>
            <td>单元格</td>
            <td>单元格</td>
            <td>单元格</td>
        </tr>
        <tr>
            <td>单元格</td>
            <td>单元格</td>
            <td>单元格</td>
        </tr>
    </table>
    
</body>
</html>